Energized anode assembly



Aug. 20, 1963 H. S. PREISER ETAL ENERGIZED ANODE ASSEMBLY FIG. I.

2 Sheets-Sheet 1 c U H II 13 ANODE BALANCING CONTROL AND METER BOX K 1 I80 LowVoltuge Lf Rectifier ADJUSTABLE l7 Volioq AC Input AC TRANSFORMER INVENTORS HERMAN S. PREISER FRANK E. COOK BORIS H. TYTELL ATTORNEY United States Patent The invention described herein may be manufactured and used by or for the Government of the United States for governmental purposes without the payment of any royalties thereon or therefor.

This application is a division of applicants copending application Serial No. 631,377, filed December 28, 1956,

now Patent No. 2,910,419, October 27, 1959, for Energized Anode Holder Assembly.

This invention relates to cathodic protection of metals against corrosion, and more particularly to cathodic protection of the underwater hull of a surface ship, submarine or the like against corrosion.

Cathodic protection techniques for corrosion control of marine structures are gradually finding widespread acceptance in marine and naval fields. riefly stated, cathodic protection is the use of an impressed direct current for reducing or suppressing electrochemical corrosion of a metallic structure immersed in an electrolyte by making the structure a cathodesfor the impressed current. The impressed current may be supplied by sacrificial galvanic anodes or by electrically energized anodes. This invention is primarily concerned with the latter system employing inert anode materials.

For a complete disclosure of the factors responsible for the corrosion of the underwater hull of a ship or, like structure reference may be had to applicants above copending application Serial No. 631,377, now Patent No. 2,910,419, October 27, 1959.

'From an examination of the factors responsible for the corrosion of the under water hull of a ship, applicants concluded that specific materials are needed for use in cathodic protection systems. The particular properties sought will depend on the end use of the material. In general, materials are needed which are nonconducting,

alkali resistant, oxy-chloride resistant, have low permeabib ity to water transmission under a potential gradient, low Water absorptivity, are nonreactive to sea water, have high strength, are impact resistant and are readilyformed into a variety of shapes. Plastic materials because of their versatility lend themselves admirably for components of cathodic protection system.

Briefly, the elements of a cathodic protection system consist of an anode; a cathode; a current source and external circuit; and measuring instruments.

The anode for impressed current systems may be a platinum-clad silver or copper rod, or an integral platinum or platinum-clad disc or gauze, a graphite rod or slab, or other shapes of inert materials such as lead and,

lead-alloys and high silicon iron alloys. The anode must "ice of chemically resistant cable sheaths and suitable cable attachment to the anode with appropriate seals.

The measuring instrument used for determining the cathodic potential of the structure is the reference elcctrode. This sensitive element must be housed in a dielectric, nonreactive, streamlined casing which is fitted with suitable cable seal-s.

.The instant invention is particularly concerned with holders for attaching and supporting disc or gauze type, rectifier energized anodes on the hull of a ship; surface or submarine.

An object of this invention is to provide an improved anode holder for use in cathodic protection systems.

Another object of the invention is to provide a streamlined anode holder.

Another object of the invention is to provide an anode holder that is dielectric.

Another object of the invention is to provide an anode holder that is resistant to alkali reactions.

Another object of the invention is to provide an anode holder that is resistant to oxy-chloride reactions.

Another object or the invention is to provide an anode holder that is light in weight, low in cost and high in mechanical strength.

Another object of the invention is to provide an anode holder wherein all mounting hardware is insulated and isolated.

A further object of the invention is to provide an anode holder wherein all except a deliberately exposed surface holder which assists in the distribution of current from the anode.

A further object of the invention is to provide an anode holder which provides relatively free and rapid circulation of an electrolyte between the anode and a cathode.

. 'A further object of the invention is to provide an anode holder assembly incorporating a connecting cable for carrying an impressed current to the anode.

A further object of the invention is to provide an integral assembly of anode, holder and current-carrying cable.

In general, the holder of the instant invention is constructed of a dielectric material, such as, a glass or nylon reinforced plastic which has been shown by test to be resistant to electrochemical reactions at the anode and cathode. Tests have shown that polyester resins resist oXy-chloricle reactions occurring at the anode and epoxy resins resist alkali reactions occurring at the cathode. The holders can be readily molded to proper shape by casting in a mold or through a laminate lay-up. process. The cloth or chopped reinforcing fiber content can be adjusted to achieve the requisite physical properties of high impact shock resistance. Where the holder fays against the hull, several coats (20 mils) of epoxy resin are applied on all holder surfaces touching or adjacent to the hull. The application of epoxyresin directly to the cured polyester forms an integral mass, chemically bonded. The nonmetallic plastic holder provides positive anode insulation. It is streamlined, is light in weight and low in cost. The holder is fastened by a welded stud arrangement on the hull. The nuts for the fastening studs are either recessed within the plastic so that they are covered over with an insulating putty or with plastic plugs, or if protruding from a flange on the holder, the nuts are covered with molded plastic caps.

Briefly, in accordance with the instant invention, a disclike, platinum-clad anode of foil thickness is supported on the hull by a polyester, glass-reinforced molded holder, with the perimeter of the disc embedded in the plastic.

In this embodiment the disc may be a foil, a gauze or a mesh.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the several views thereof, and wherein:

FIG. 1 shows a schematic wiring diagram for an irn pressed current cathodic protection system in accordance with this invention;

a FIG. 2 is an enlarged plan view of a holder for a platinum-clad, disc anode in accordance with the instant invention; and

FIG. 3 is a trans-verse section taken substantially on line 3-3 of FIG. 2. 7

Referring first to FIG. 1, which illustrates a cathodic protection system wherein an impressed current is supplied by rectifier energized anodes, the numeral 10 designates the hull of a surface ship protected by a plurality of anodes 2t) spaced around the sides and stem thereof. As pointed out in detail hereinafter, each of the anodes is shielded from the hull by a dielectric shield or blanket ll. Each of the anodes is connected by a conductor 12 to an anode balancing control and meter box 13, which purpose is for measuring current output of each anode and for balancing dilferences in line resistance. Control 13 is connected by a conductor 14 to the positive side of a low voltage rectifier 15, while the negative side of the rectifier is grounded to the hull of the vessel by a conductor '16 thereby making the hull the cathode of the low voltage circuit. A pair of conductors 17a and 17b connect opposite sides of the rectifier to the low voltage A.C.'output of electrical energy from an adjustable transformer 18 which is fed by an A.C. input 18a. Reference electrodes 19 are suitably mounted on the hull at least twenty-five feet from the nearest anode and are connected to a suitable potentiometer, not shown, for determining the polarization of the hull. Based on readings taken by the reference electrodes, adjustment can be made in the transformer 1 8 to change the current output to the anodes to correspond to the proper value. Reference electrodes (AgAgOl) readings below .80 volt require an increase in the anode current, and readings above -.80 volt require a decrease in the anode current. The electric circuits, illustrated in FIG. '1, are not per se a part of this invention and therefore need not be described in further detail. *It being sufficient to state that by these circuits a controlled low voltage current flows from the rectifier to the several anodes. and from these through the sea water to the hull and back to the rectifier.

Referring now to FIGS. 2 and 3, in accordance with the instant invention, the anode assembly, indicated generally by reference numeral 20; includes a plastic holder 21 and an inert, platinum foil anode 22. The anode is in the form of a disc with the perimeter thereof bent inward, forming a circular flange 22a that is embedded in the holder. At the center, the anode is formed with a smooth circular portion 220, to the back surface of which is welded a platinum-clad or other precious metal backing piece 23. Between the center and the flange portions, the disc is indented to form a grid-like structure indicated in exaggerated form at 2212. This indenting or scoring of the anode surface provides anchorage to the plastic holder and it lowers surface resistance because of easy release of gaseous products. Prior to embedding the anode 22 in the plastic holder, a platinum-clad prong 24 is welded to the backing piece 243. The prong 24 is coated with a liquid polyester resin over which is placed a glass reinforced polyester sleeve 2 4a. The sleeve 24a covers the entire length of the prong except for an exposed tip 24b, which tip is of substantially the same outside diameter as that of the polyester sleeve.

With the anode shaped and assembled in the manner described, the disc is then embedded in the plastic holder by cutting the plastic around the disc, leaving only the outer surface of the smooth center and indented portions exposed. Thus an assembly of holder and anode is formed that is circular in plan, streamlined and of wafer thickness. The indented or roughened disc, which is of foil thickness may be replaced by platinum gauze or mesh.

A circular sole plate .26, of substantially the same diameter as that of the plastic holder is welded at its periphery to the hull 10 by a circular weld 27. As shown in section in FIG. 3, the weld 27 is ground smooth to the streamline contour of the sloping surface of the holder. The sole plate is provided with a beveled circular opening in its center for the reception of a collar 28 of a stuffing tube 29. Collar 28 is of the same thickness as the sole plate and the space between the periphery of the collar and the beveled surface of the sole plate is filled with a weld 30, the outer surface of which weld is round smooth to the level of the sole plate and collar.

The stufiing tube, shown schematically in FIG. 3, projects through an opening in the hull to the interior thereof and is welded thereto as at 31. A female connector 3-2 is located within the smiling tube in position to receive the exposed, platinum-clad tip 24b of prong 24, and the connector forms the terminal of the current-carrying cable 12 (FIGS. 1 and 3) that passes through a gland nut 34, screw threaded into the stuffing tube. The current-carrying cable is connected to the source of low-voltage current as shown in FIG. 1.

Prior to attaching the anode assembly to the hull of the vessel, the neoprene shield 11 is applied to the hull in the manner described in applicants parent application Serial No. 631,377. Then the anode assembly is attached to the hull by means of a plurality of screws 38 that are threaded into tapped, spaced openings in the sole plate. After the screws have been driven home, each of the heads thereof is covered by a plastic material 39, streamlined to the contour of the holder. As shown in FIG. 3, the contour of the exposed surface of the holder is such as to prevent damage to the anode by dragging ropes or the like while still not interfering with the free passage of sea water into contact with the anode. As shown in FIG. 3, the only metal exposed to sea water is the platinum anode. If desired, the attaching screws 38 may be replaced by studs and nuts and a cushioning rubber pad may be inserted between the anode holder and the hull, as described in connection with the other embodiments of the invention disclosed in applicants parent application Serial No. 631,377.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and, although the invention has been illustrated and described in connection with particular details of construction and the particular materials specific to the instant embodiment of the invention, the details of construction and the particular materials may be modified and/ or interchanged without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. An integral anode assembly for use in impressed current cathodic protection systems for underwater proteotion of the bulls of ships and the like comprising, an inert anode, said anode being formed of a platinum disc of foil thickness, said disc having a grid like surface on the face thereof to facilitate the release of gaseous products of electrolysis, a streamline holder for the anode, said holder being formed of dielectric, anticorrosive, chem ically resistant plastic resin and having a cavity in one surface thereof for reception of the anode, means interconnecting said anode, said holder and said hull, said means comprising means for anchoring the anode disc within the cavity of the holder with one major surface of the disc exposed to ambient sea water, said anode holder being provided with a hole extending through the thickness thereof whereby electrical contact can be made, between the under surface of the platinum disc and the current source of the cathodic protection system and means for insulatedly attaching the holder to the hull.

2. An integral anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an inert anode, said anode being formed of a platinumdisc of foil thickness, said disc having a grid like surface on the face thereof to facilitate the release of gaseous products of electrolysis, a streamline holder [for the anode, said holder being formed of dielectric, anticorrosive, chemically resistant plastic resin and having a cavity therein for reception of the anode, a peripheral portion of said anode being embedded in and bonded to said holder adjacent the periphery of said cavity, whereby the anode disc is anchored Within said cavity in the holder with a major portion of one surface of the disc being exposed to ambient sea water, said anode holder being provided with a hole extending through the thickness thereof whereby electrical contact can be made between the under surface of the platinum disc and the current source of the cathodic protection system, and means interconnecting said holder and said hull, said means comprising means for insulatedly attaching the holder to the hull.

3. An integral anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an

inert anode, :said anode being formed of a platinum disc of foil thickness, said disc having a grid like surface on the face thereof to facilitate the release of gaseous products of electrolysis, a streamline holder for the anode, said holder being formed of dielectric, anticorrosive, chemically resistant plastic resin and having a cavity in one surface thereof for reception of the anode, one surface of said disc being bonded to said holder at the bottom of said cavity and a peripheral flange on the disc embedded in, and bonded to said holder adjacent the periphery of said cavity, said anode holder being provided with a hole extending through the thickness thereof whereby electrical contact can be made between the under surface or the platinum-disc and the current source of the cathodic protection system, and means interconnecting said holder and said hull, said means comprising means for insulatedly attaching the holder to the hull.

4. An integral anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an inert anode, said anode being formed as a platinum disc of foil thickness, said disc having a grid like surface on the face thereof to facilitate the release of gaseous prodnets of electrolysis, a streamline holder for the anode, such holder being formed of dielectric, anticorrosive chemically resistant plastic resin and having a cavity therein for reception of the anode, a peripheral portion of said anode being embedded in and bonded to said holder adjacent the outer edge of said cavity, whereby the anode disc is anchored within said cavity in the holder with a major portion of one surface of the disc being juxtaposed to ambient sea water, said anode holder being provided with a hole extending through the thickness thereof whereby electrical contact can be made between the under surface of the platinum disc and the current source of the cathodic protection system, means interconnecting said holder and said hull, said means comprising means for attaching the holder to the hull, and a sheet of dielectric, ianticorrosive chemically resistive plastic material interposed between said holder and said hull and extending beyond the periphery of the holder whereby the holder is insulated from the hull of the ship.

5. An anode assembly for use in impressed current cathodic protection systems for underwater protection for the hulls of ships and the like, comprising an anode 6 holder, an inert anode mounted in said holder, said anode being formed of a platinum foil disc, and said holder being formed of polyester resin plastic and having a cavity in one surface thereof for reception of the anode, and said platinum foil disc having a smooth central surface for attachment to a backing plate, an intermediate surfaceroughencd on one side for attachment to the holder and on the opposite side to facilitate easy release of gaseous products from ambient seawater medium and a flanged periphery for attachment to the holder, said holder ineluding a circular member substantially or wafer thickness and having the flange portion of the platinum foil disc embedded in the plastic, and means interconnecting said holder and said hull, said means comprising means for insulatingly attaching the holder to the hull.

6. An anode assembly as set forth in claim 5 wherein the anode includes a backing plate secured at one side thereof to the smooth center surface of the platinum foil disc, a current-carrying platinum-clad prong secured at one end to the opposite side of the backing plate and having a platinum clad tip on the opposite end thereof for contact with a current-carrying cable, and a plastic sleeve surrounding the length of the prong between the backing plate and the platinum-clad tip.

7. An anode assembly for use in impressed current cathodic protection systems for underwater protection of the hulls of ships and the like comprising, an anode holder, an inert anode mounted in said holder, said anode being formed of a platinum disc, and said holder being formed of dielectric anti-corrosive, chemically resistant plastic resin and having a cavity in one surface thereof for reception of the anode, said platinum disc comprising a platinum foil disc having a smooth central surface for attachment to a backing plate, an intermediate surface roughened on one face for bonding to said holder and on the opposite face to facilitate the release of gaseous products from ambient seawater medium, one surface of said disc being bonded to said holder at the bottom of said cavity and a peripheral flange on the disc embedded in and bonded to said holder adjacent the periphery of said cavity, and means interconnecting said holder and said hull, said means comprising means for insulatingly attachin g the holder to the hull.

8. An anode assembly as set forth in claim 7 wherein the anode includes a backing plate secured at one side thereof to the smooth central surface of the platinum foil disc, a current-carrying platinum clad prong secured at one end to the opposite side of the backing plate and having a platinum clad tip on the opposite end thereof for contact with a current carrying cable, and a plastic dielectric sleeve surrounding the length of the prong between the backing plate and the platinum clad tip.

References (Jilted in the file of this patent UNITED STATES PATENTS 791,457 Dion June 6, 1905 1,506,306 Kirkaldy ..1 Aug. 26, 1924 1,833,806 Weber et a1 Nov. 24, 1931 1,900,011 Durham Mar. 7, 1933 2,752,308 Andrus June 26, 1956 2,776,940 Oliver Jan. 8, 1957 2,776,941 Wagner Jan. 8, 1957 2,856,342 Vander Hoevenet a1 Oct. 14, 1958 2,863,819 Preiser Dec. 9, 1958 2,878,173 Obermann Mar. 17, 1959 2,890,160 Hunting et al. June 9', 1959 3,019,177 Anderson Jan. 30, 1962 FOREIGN PATENTS 188,957 Great Britain Nov. 22, 1923 614,799 Great Britain Dec. 22, 1948 749,636 France July 27, 19 33 

1. AN INTEGRAL ANODE ASSEMBLY FOR USE IN IMPRESSED CURRENT CATHODIC PROTECTION SYSTEMS FOR UNDERWATER PROTECTION OF THE HULLS OF SHIPS AND THE LIKE COMPRISING, AN INERT ANODE, SAID ANODE BEING A FORMED OF A PLATINUM DISC OF FOIL THICKNESS, SAID DISC HAVING A GRID LIKE SURFACE ON THE FACE THEREOF TO FACILITATE THE RELEASE OF GASEOUS PRODUCTS OF ELECTROLYSIS, A STREAMLINE HOLDER FOR THE ANODE, SAID HOLDER BEING FORMED OF DIELECTRIC, ANTICORROSIVE, CHEMICALLY RESISTANT PLASTIC RESIN AND HAVING A CAVITY IN ONE SURFACE THEREOF FOR RECEPTION OF THE ANODE, MEANS INTERCONNECTING SAID ANODE, SAID HOLDER AND SAID HULL, SAID MEANS COMPRISING MEANS FOR ANCHORING THE ANODE DISC WITHIN THE CAVITY OF THE HOLDER WITH ONE MAJOR SURFACE OF THE DISC EXPOSED TO AMBIENT SEA WATER, SAID ANODE HOLDER BEING PROVIDED WITH A HOLE EXTENDING THROUGH THE THICKNESS THEREOF WHEREBY ELECTRICALLY CONTACT CAN BE MADE BETWEEN THE UNDER SURFACE OF THE PLATINUM DISC AND THE CURRENT SOURCE OF THE CATHODIC PROTECTUON SYSTEM AND MEANS FOR INSULATEDLY ATTACHING THE HOLDER TO THE HULL. 